This project investigates the spatial distribution of genetic variation at mitochondrial and micro-satellite loci for the yellow fever mosquito, Aedes aegypti, in South Florida. Aedes aegypti is a container-dwelling mosquito that is a major vector of yellow fever and dengue viruses. Dispersal, colonization, and re-colonization (e.g., following control efforts) by Aedes aegypti are thus crucial processes for understanding population structure of this extremely important species, and for understanding its potential for spreading, which may erode local vector control efforts and potentially impact human health. We combine molecular population genetics, phylogeography, landscape ecology, and GIS to test two hypotheses about dispersal, gene flow, and population structure of Ae. aegypti in S. Florida. HYPOTHESIS 1: Container permanence and human transport affect genetic structure and dispersal pattern of Aedes aegypti at the scale of the urban area. To test this hypothesis, we will quantify differences in gene flow patterns arising from different amounts of natural and human-aided dispersal for populations found in permanent vs. ephemeral containers in Tampa and Miami. HYPOTHESIS 2: Dispersal corridors and barriers determined by human land use affect gene flow patterns in Aedes aegypti at the scale of the Florida peninsula. To test this hypothesis we will conduct a phylogeographic analysis of Ae. aegypti populations on the east and west coasts of south Florida, applying the tools of GIS and correlating our measures of genetic and geographis distances among populations. This proposed work is significant because: 1) It will contribute to the understanding of dispersal, gene flow, and colonization of this very important vector, and indicate likely dispersal routes and geographic scale over which re-colonization (e.g., after eradication) may occur. A subtropical climate and human immigration from the tropics make Florida the area of the continental US most likely to become a focus for Ae. aegypti borne viruses. 2) It will provide a model for approaches to investigating similar questions for other mosquitoes within human dominated landscapes. Our geographic sampling strategy, use of differentially informative mtDNA and microsatellite DMA markers, integration of GIS analysis, and explicit testing of hypotheses about patterns of gene flow can be generalized to address similar questions for other mosquitoes.